/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.net.io;

import java.util.EventListener;

/**
 * Accepts {@link CopyStreamEvent}s to track the progress of a stream copying operation. However, it is currently not used that way within Net for performance
 * reasons. Rather, the bytesTransferred(long, int) method is called directly rather than passing an event to bytesTransferred(CopyStreamEvent), saving the
 * creation of a CopyStreamEvent instance. Also, the only place where CopyStreamListener is currently used within Net is in the static methods of the
 * uninstantiable org.apache.commons.io.Util class, which would preclude the use of addCopyStreamListener and removeCopyStreamListener methods. However, future
 * additions may use the JavaBean event model, which is why the hooks have been included from the beginning.
 *
 * @see CopyStreamEvent
 * @see CopyStreamAdapter
 * @see Util
 */
public interface CopyStreamListener extends EventListener {
    /**
     * Accepts a source event after copying a block of bytes from a stream. The CopyStreamEvent will contain the total number of bytes transferred so far and
     * the number of bytes transferred in the last write.
     *
     * @param event The CopyStreamEvent fired by the copying of a block of bytes.
     */
    void bytesTransferred(CopyStreamEvent event);

    /**
     * This method is not part of the JavaBeans model and is used by the static methods in the org.apache.commons.io.Util class for efficiency. It is invoked
     * after a block of bytes to inform the listener of the transfer.
     *
     * @param totalBytesTransferred The total number of bytes transferred so far by the copy operation.
     * @param bytesTransferred      The number of bytes copied by the most recent write.
     * @param streamSize            The number of bytes in the stream being copied. This may be equal to CopyStreamEvent.UNKNOWN_STREAM_SIZE if the size is
     *                              unknown.
     */
    void bytesTransferred(long totalBytesTransferred, int bytesTransferred, long streamSize);
}
